Facade Design Pattern

// Facade pattern -- Structural example

using System;

namespace DoFactory.GangOfFour.Facade.Structural
{

  // Mainapp test application

  class MainApp
  {
    public static void Main()
    {
      Facade facade = new Facade();

      facade.MethodA();
      facade.MethodB();

      // Wait for user
      Console.Read();
    }
  }

  // "Subsystem ClassA"

  class SubSystemOne
  {
    public void MethodOne()
    {
      Console.WriteLine(" SubSystemOne Method");
    }
  }

  // Subsystem ClassB"

  class SubSystemTwo
  {
    public void MethodTwo()
    {
      Console.WriteLine(" SubSystemTwo Method");
    }
  }

  // Subsystem ClassC"

  class SubSystemThree
  {
    public void MethodThree()
    {
      Console.WriteLine(" SubSystemThree Method");
    }
  }

  // Subsystem ClassD"

  class SubSystemFour
  {
    public void MethodFour()
    {
      Console.WriteLine(" SubSystemFour Method");
    }
  }

  // "Facade"

  class Facade
  {
    SubSystemOne one;
    SubSystemTwo two;
    SubSystemThree three;
    SubSystemFour four;

    public Facade()
    {
      one = new SubSystemOne();
      two = new SubSystemTwo();
      three = new SubSystemThree();
      four = new SubSystemFour();
    }

    public void MethodA()
    {
      Console.WriteLine("\nMethodA() ---- ");
      one.MethodOne();
      two.MethodTwo();
      four.MethodFour();
    }

    public void MethodB()
    {
      Console.WriteLine("\nMethodB() ---- ");
      two.MethodTwo();
      three.MethodThree();
    }
  }
}    

using System;

namespace DoFactory.GangOfFour.Facade.RealWorld
{
  // MainApp test application

  class MainApp
  {
    static void Main()
    {
      // Facade
      Mortgage mortgage = new Mortgage();

      // Evaluate mortgage eligibility for customer
      Customer customer = new Customer("Ann McKinsey");
      bool eligable = mortgage.IsEligible(customer,125000);
      
      Console.WriteLine("\n" + customer.Name +
          " has been " + (eligable ? "Approved" : "Rejected"));

      // Wait for user
      Console.Read();
    }
  }

  // "Subsystem ClassA"

  class Bank
  {
    public bool HasSufficientSavings(Customer c, int amount)
    {
      Console.WriteLine("Check bank for " + c.Name);
      return true;
    }
  }

  // "Subsystem ClassB"

  class Credit
  {
    public bool HasGoodCredit(Customer c)
    {
      Console.WriteLine("Check credit for " + c.Name);
      return true;
    }
  }

  // "Subsystem ClassC"

  class Loan
  {
    public bool HasNoBadLoans(Customer c)
    {
      Console.WriteLine("Check loans for " + c.Name);
      return true;
    }
  }

  class Customer
  {
    private string name;

    // Constructor
    public Customer(string name)
    {
      this.name = name;
    }

    // Property
    public string Name
    {
      get{ return name; }
    }
  }

  // "Facade"

  class Mortgage
  {
    private Bank bank = new Bank();
    private Loan loan = new Loan();
    private Credit credit = new Credit();

    public bool IsEligible(Customer cust, int amount)
    {
      Console.WriteLine("{0} applies for {1:C} loan\n",
        cust.Name, amount);

      bool eligible = true;

      // Check creditworthyness of applicant
      if (!bank.HasSufficientSavings(cust, amount))
      {
        eligible = false;
      }
      else if (!loan.HasNoBadLoans(cust))
      {
        eligible = false;
      }
      else if (!credit.HasGoodCredit(cust))
      {
        eligible = false;
      }

      return eligible;
    }
  }
}

// Facade pattern -- .NET optimized

Two editions: C# and VB.NET

This .NET code is part of our unique Design Pattern Framework 2.0TM with: 69 gang-of-four pattern projects 46 head-first pattern projects Martin Fowler's enterprise patterns SOA design patterns e-commerce web application 100% pure source code Instant download. Order now!

         See our Singleton page for a .NET optimized code sample.